1. Field of the Invention
The present invention relates to a method of manufacturing a member having a toothed portion, and in particular to a method of manufacturing a clutch housing or a clutch hub for an automatic transmission used in an automobile or the like.
2. Description of the Related Art
A clutch housing incorporates therein a clutch unit composed of a plurality of friction plates and separator plates. The clutch housing is formed at its inner periphery with toothed portions which serve as splines on which the friction plates and the separator plates are fitted so as to be axially displaceable.
Further, a clutch hub is formed on its outer peripheral surface with tooth-formed portions which serve as splines on which the friction plates and the separators are fitted so as to be axially displaceable.
A plurality of toothed portions which are extended in the axial direction of the clutch housing or the clutch hub, and which are arranged circumferentially thereof, have to be formed with a required degree of accuracy so as to allow the friction plates and the separator plates to be smoothly displaced in the axial direction. Thus, in order to finish up the toothed portions so as to have desired axial dimensions, the toothed portions are subjected to cutting and shear-trimming in order to have appropriate dimensions and are thereafter deburred.
Conventionally, the toothed portions have been subjected to cutting and shear-trimming, after axial formation of teeth, so as to have appropriate dimensions, and thereafter subjected to deburring.
However, since the toothed portion has a formed surface having a relatively complicated tooth shape, a manufacture method as disclosed in, for example, Japanese Patent Laid-Open No. H06-193647, has raised several problems such as follows:
At first, since the cutting is intermittent cutting while the shear-trimming is of an index type, and therefore, the following problems are caused:    (1) a long cycle time;    (2) requirement of an exclusive jig;    (3) requirement of labor for stabilizing a deburring quality due to increased work load during deburring.The above-mentioned problems cause an increase in manufacturing costs, directly or indirectly.
Further, conventionally, there have been carried out intermittent cutting and index type shear-trimming after formation of teeth, and then deburring in order to finish up the toothed portion so as to have teeth with appropriate axial dimensions. However, the above-mentioned process steps are likely to cause a bottle neck problem which results in hindrance to enhancement of a productivity and stabilization of a quality. In particular, in the method disclosed in Japanese Patent Laid-Open No. H06-193647, teeth have to be formed by a cam mechanism after end-surface pressing, and accordingly, two process steps are required.